U.S. patent number 5,230,371 [Application Number 07/829,985] was granted by the patent office on 1993-07-27 for papermakers fabric having diverse flat machine direction yarn surfaces.
This patent grant is currently assigned to Asten Group, Inc.. Invention is credited to Henry J. Lee.
United States Patent |
5,230,371 |
Lee |
July 27, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Papermakers fabric having diverse flat machine direction yarn
surfaces
Abstract
A papermakers fabric having a stacked system of flat
monofilament machine direction yarns (hereinafter MD yarns) which
define the surface characteristics of the fabric. The system of MD
yarns comprises upper and lower yarns which are vertically stacked.
Preferably, the upper MD yarns define floats on the upper surface
of the fabric and each upper MD yarn is paired in a vertically
stacked orientation with a lower MD yarn. The upper MD yarns may be
comprised of one type of material, such as nylon 6, 6 to define a
hydrolysis resistance paper carrying surface with the lower MD
yarns, which define the machine side surface, being made of a
polyester (PET) yarns, which are lower in cost and are less
hydrolysis resistant. Cross machine direction yarns (hereinafter
CMD yarns) may be a third type of yarn, for example a relatively
inert material such as Ryton.TM.. The CMD yarns are protected from
abrasive wear by the upper and lower MD yarns. The stacked flat MD
yarn construction permits a variety of other variations to provide
different surface characteristics to the opposing sides of the
fabric. Yarn dimensions may be varied to provide a wide range of
permeability for fabrics using such a stacked MD yarn construction.
Also float length can be varied between the upper and lower MD yarn
weaves to impart different surface characteristics.
Inventors: |
Lee; Henry J. (Summerville,
SC) |
Assignee: |
Asten Group, Inc. (Charleston,
SC)
|
Family
ID: |
27504647 |
Appl.
No.: |
07/829,985 |
Filed: |
February 3, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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534164 |
Jun 6, 1990 |
5103874 |
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654008 |
Feb 14, 1991 |
5117865 |
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567974 |
Aug 15, 1990 |
5092373 |
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Current U.S.
Class: |
139/383A;
139/383AA; 442/213; 442/216 |
Current CPC
Class: |
D21F
1/0036 (20130101); D21F 1/0054 (20130101); D21F
7/083 (20130101); Y10T 442/326 (20150401); Y10T
442/3285 (20150401) |
Current International
Class: |
D21F
7/08 (20060101); D21F 1/00 (20060101); D03D
013/00 (); D03D 015/00 () |
Field of
Search: |
;139/383A,383AA
;162/DIG.1 ;428/222,225 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0144592 |
|
Sep 1984 |
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EP |
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0211426 |
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Aug 1986 |
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EP |
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2407291 |
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May 1979 |
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FR |
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Primary Examiner: Falik; Andrew M.
Attorney, Agent or Firm: Volpe and Koenig
Parent Case Text
This application is a continuation-in-part of my copending
applications Ser. No. 07/534,164, filed Jun. 6, 1990, Papermakers
Fabric WITH STACKED MACHINE DIRECTION YARNS U.S. Pat. No.
5,103,874; Ser. No. 07/654,008, filed Feb. 14, 1991, PAPERMAKERS
FABRIC WITH FLAT HIGH ASPECT RATIO YARNS U.S. Pat. No. 5,117,865;
and Ser. No. 07/567,974, filed Aug. 15, 1990, PAPERMAKERS FABRIC
WITH ORTHOGONAL MACHINE DIRECTION YARN SEAMING LOOPS U.S. Pat. No.
5,092,373.
Claims
What I claim is:
1. A papermakers fabric having a single layer of CMD yarns and a
system of flat monofilament MD yarns interwoven with said CMD yarns
in a selected repeat pattern, wherein the MD yarn system is
comprised of paired upper and lower yarns stacked in the same
relative vertical alignment to each other throughout the body of
the fabric and wherein the combination of the weave repeat, yarn
size and shape, and material composition of the upper MD yarns
differs from the combination of the weave repeat, yarn size and
shape, and material composition of the lower MD yarns such that the
upper MD yarns and the lower MD yarns impart different surface
characteristics to the opposing sides of the fabric by dominating
both of the opposing sides.
2. The fabric of claim 1 wherein the at least some of the upper MD
yarns are a first type of material and at least some of the lower
MD yarns are a second different type of material.
3. The fabric of claim 2 wherein the upper MD yarns include yarns
which are more hydrolysis resistant than the lower MD yarns.
4. The fabric of claim 2 wherein the weave repeat and yarn size and
shape are the same for both the upper and lower MD yarns.
5. The fabric of claim 3 wherein the upper MD yarns are nylon and
the lower MD yarns are polyester (PET).
6. The fabric of claim 2 wherein at least some of the CMD yarns are
a third different type of material.
7. The fabric of claim 6 wherein the upper MD yarns are nylon, the
lower MD yarns are polyester (PET) and the CMD yarns are
polyphenylene sulfide (PPS).
8. The fabric of claim 7 wherein:
the upper and lower MD yarns are both 0.25 mm by 1.06 mm, woven
with surface floats and woven 100% warp fill, and
the CMD yarns alternate 0.80 mm and 0.55 mm in diameter, woven
16-22 yarns per inch such that the fabric has a permeability of
70-150 cfm.
9. The fabric of claim 7 wherein:
the upper and lower MD yarns are both 0.30 mm by 0.80 mm, woven
with surface floats and woven about 75% warp fill, and
the CMD yarns alternate 0.80 mm and 0.50 mm in diameter, woven
16-24 yarns per inch such that the fabric has a permeability of
200-400 cfm.
10. The fabric of claim 1 wherein the cross-sectional dimensions of
the upper MD yarns differ from the cross-sectional dimensions of
the lower MD yarns.
11. The fabric of claim 1 wherein at least one side of the fabric
has MD yarn surface floats which span more CMD yarns than the MD
yarns which define the opposing fabric surface.
12. The fabric of claim 1 wherein selected upper MD yarns loop back
and interweave with the CMD yarns directly beneath themselves to
define series of orthogonal seaming loops on opposing ends of said
fabric.
13. The fabric of claim 1 wherein selected lower MD yarns loop back
and interweave with the CMD yarns directly beneath themselves to
define series of orthogonal seaming loops on opposing ends of said
fabric.
14. An industrial fabric including a multi-layer system of CMD
yarns and a system of flat monofilament MD yarns interwoven with
said CMD yarns in a selected repeat pattern, the MD yarn system
comprising closely woven paired-upper and lower yarns stacked in
the same relative vertical alignment to each other throughout the
body of the fabric, the upper MD yarns interweaving with at least
two layers of CMD yarns, the lower MD yarns interweaving with at
least two layers of CMD yarns, and the combination of the weave
repeat, yarn size and shape, and material composition of the upper
MD yarns differing from the combination of the weave repeat, yarn
size and shape, and material composition of the lower MD yarns such
that the upper MD yarns and the lower MD yarns impart different
surface characteristics to the opposing sides of the fabric.
15. The fabric of claim 14 wherein the at least some of the upper
MD yarns are a first type of material and at least some of the
lower MD yarns are a second different type of material.
16. The fabric of claim 15 wherein the upper MD yarns include yarns
which are more hydrolysis resistant than the lower MD yarns.
17. The fabric of claim 15 wherein the weave repeat and yarn size
and shape are the same for both the upper and lower MD yarns.
18. The fabric of claim 16 wherein the upper MD yarns are nylon and
the lower MD yarns are polyester (PET).
19. The fabric of claim 15 wherein at least some of the CMD yarns
are a third different type of material.
20. The fabric of claim 19 wherein the upper MD yarns are nylon,
the lower MD yarns are polyester (PET) and the CMD yarns of
polyphenylene sulfide (PPS).
21. The fabric of claim 20 wherein:
the upper and lower MD yarns are both 0.25 mm by 1.06 mm, woven
with surface floats and woven 100% warp fill, and
the CMD yarns alternate 0.80 mm and 0.55 mm in diameter, woven
16-22 yarns per inch such that the fabric has a permeability of
70-150 cfm.
22. The fabric of claim 20 wherein:
the upper and lower MD yarns are both 0.30 mm by 0.80 mm, woven
with surface floats and woven about 75% warp fill, and
the CMD yarns alternate 0.80 mm and 0.50 mm in diameter, woven
16-24 per inch such that the fabric has a permeability of 200-400
cfm.
23. The fabric of claim 14 wherein the cross-sectional dimensions
of the upper MD yarns differ from the cross-sectional dimensions of
the lower MD yarns.
24. The fabric of claim 14 wherein at least one side of the fabric
has MD yarn surface floats which span more CMD yarns than the MD
yarns which define the opposing fabric surface.
25. The fabric of claim 14 wherein selected upper MD yarns loop
back and interweave with the CMD yarns directly beneath themselves
to define series of orthogonal seaming loops on opposing ends of
said fabric.
26. The fabric of claim 14 wherein selected lower MD yarns loop
back and interweave with the CMD yarns directly beneath themselves
to define series of orthogonal seaming loops on opposing ends of
said fabric.
Description
The present invention relates to papermakers fabrics and in
particular to fabrics comprised of flat monofilament yarns.
BACKGROUND OF THE INVENTION
Papermaking machines generally are comprised of three sections:
forming, pressing, and drying. Papermakers fabrics are employed to
transport a continuous paper sheet through the papermaking
equipment as the paper is being manufactured. The requirements and
desirable characteristics of papermakers fabrics vary in accordance
with the particular section of the machine where the respective
fabrics are utilized.
With the development of synthetic yarns, shaped monofilament yarns
have been employed in the construction of papermakers fabrics. For
example, U.S. Pat. No. 4,290,209 discloses a fabric woven of flat
monofilament warp yarns; U.S. Pat. No. 4,755,420 discloses a
non-woven construction where the papermakers fabric is comprised of
spirals made from flat monofilament yarns.
Numerous weaves are known in the art which are employed to achieve
different results. For example, U.S. Pat. No. 4,438,788 discloses a
dryer fabric having three layers of cross machine direction yarns
interwoven with a system of flat monofilament machine direction
yarns such that floats are created on both the top and bottom
surfaces of the fabric. The floats tend to provide a smooth surface
for the fabric.
Permeability is an important criteria in the design of papermakers
fabrics. In particular, with respect to fabrics made for running at
high speeds on modern drying equipment, it is desirable to provide
dryer fabrics with relatively low permeability.
U.S. Pat. No. 4,290,209 discloses the use of flat monofilament warp
yarns woven contiguous with each other to provide a fabric with
reduced permeability. However, even where flat warp yarns are woven
contiguous with each other, additional means, such as stuffer
yarns, are required to reduce the permeability of the fabric. As
pointed out in that patent, it is desirable to avoid the use of
fluffy, bulky stuffer yarns to reduce permeability which make the
fabric susceptible to picking up foreign substances or retaining
water.
U.S. Pat. Nos. 4,290,209 and 4,755,420 note practical limitations
in the aspect ratio (cross-sectional width to height ratio) of
machine direction warp yarns defining the structural weave of a
fabric. The highest practical aspect ratio disclosed in those
patents is 3:1, and the aspect ratio is preferably, less than
2:1.
U S. Pat. No. 4,621,663, assigned to the assignee of the present
invention, discloses one attempt to utilize high aspect ratio yarns
(on the order of 5:1 and above) to define the surface of a
papermakers dryer fabric. As disclosed in that patent, a woven base
fabric is provided to support the high aspect ratio surface yarns.
The woven base fabric is comprised of conventional round yarns and
provides structural support and stability to the fabric disclosed
in that patent.
U.S. Pat. No 4,815,499 discloses the use of flat yarns in the
context of a forming fabric. That patent discloses a composite
fabric comprised of an upper fabric and a lower fabric tied
together by binder yarns. The aspect ratio employed for the flat
machine direction yarns in both the upper and lower fabrics are
well under 3:1.
In use, papermakers fabrics are configured as endless belts.
Weaving techniques are available to initially weave fabrics
endless. However, there are practical limitations on the overall
size of endless woven fabrics as well as inherent installation
difficulties. Moreover, not all papermaking equipment is designed
to accept the installation of an endless fabric.
Flat woven fabrics are often supplied having opposing ends which
are seamed together during installation of the fabric on
papermaking equipment. Usually one end of the fabric is threaded
through the serpentine path defined by the papermaking equipment
and is then joined to its opposing end to form a continuous
belt.
A variety of seaming techniques are well known in the art. One
conventional method of seaming is to form the machine direction
yarns on each end of the fabric into a series of loops. The loops
of the respective fabric ends are then intermeshed during fabric
installation to define a channel through which a pintle is inserted
to lock the ends together.
For example, U.S. Pat. Nos. 4,026,331; 4,438,789; 4,469,142;
4,846,231; 4,824,525 and 4,883,096 disclose a variety of pin seams
wherein the machine direction yarns are utilized to form the end
loops. In each of those patents, however, the machine direction
yarn projects from the end of the fabric and weaves back into the
fabric adjacent to itself. Accordingly, the loops inherently have a
twist or torque factor and are not entirely orthogonal to the plane
of the fabric. U.S. Pat. No. 4,883,096 specifically addresses this
problem.
It would be desirable to provide a papermakers fabric with machine
direction seaming loops which do not have torque and/or twist.
Additionally, the opposing sides of a papermakers fabric generally
serve distinct functions. One side being utilized to carry the
aqueous paper web; the other side being in contact with the various
rolls and other mechanisms of the papermaking machine. It would be
desirable to provide a true two-sided dual characteristic
papermakers fabric designed to facilitate the distinct requirements
for the opposing fabric sides.
SUMMARY AND OBJECTS INVENTION
The present invention provides a papermakers fabric having a system
of flat monofilament machine direction yarns (hereinafter MD yarns)
which are stacked to control the permeability of the fabric. The
present weave also provides for usage of high aspect ratio yarns as
structural weave components. The system of MD yarns comprises upper
and lower yarns which are vertically stacked. Preferably, the upper
MD yarns define floats on the upper surface of the fabric and each
upper MD yarn is paired in a vertically stacked orientation with a
lower MD yarn. The lower MD yarns may weave in an inverted image of
the upper MD yarns to provide floats on the bottom fabric surface
or may weave with a different repeat to provide a different surface
on the bottom of the fabric.
The upper MD yarns may be flat monofilament yarns woven contiguous
with each other to reduce the permeability of the fabric and to
lock in the machine direction alignment of the stacking pairs of MD
yarns. A stacked, contiguous closely woven machine direction system
provides stability and permits the MD yarns to have a relatively
high aspect ratio, cross-sectional width to height, of greater than
3:1. Machine direction yarns further define a series of orthogonal
seaming loops on the opposing fabric ends. End segments of the
lower MD yarns are removed and the upper MD yarn ends are looped
back upon themselves and rewoven into the fabric end in the space
vacated by the trimmed lower MD yarn end segments. The lower MD
yarns may weave in an inverted image of the upper MD yarns such
that the crimp of the upper MD yarns conforms with the lower MD
yarn weave pattern space into which the upper MD yarn ends are
backwoven. This improves the strength of the seam.
Non-loop forming upper MD yarns are also preferably backwoven into
the space vacated by trimming the respective lower MD yarns. The
upper MD yarns may be woven contiguous with each other to lock in
the machine direction alignment of the stacking pairs of MD yarns
and the orthogonal orientation of the end loops.
In the preferred embodiment, the same type of material and the same
geometric shape and size yarns are used throughout each layer of
the machine direction yarn system. However, different yarns are
used for the top and the bottom MD yarns, respectively, to impart
different characteristics to the top and bottom surfaces of the
fabric through the domination of the MD yarns on the respective
fabric sides as seen for example in FIG. 11. In particular, when
such diverse MD yarn layers are woven with a single layer of CMD
yarns, the result is a true two-sided dual characteristic
papermakers fabric.
It is an object of the invention to provide a two-sided dual
characteristic papermaker's fabric.
It is also an object of the invention to provide a papermakers
fabric having permeability controlled with woven flat machine
direction yarns.
It is a further object of the invention to provide a low
permeability fabric constructed of all monofilament yarns without
the use of bulky stuffer yarns and without sacrificing strength or
stability.
Other objects and advantages will become apparent from the
following description of presently preferred embodiments.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of a papermakers fabric made in
accordance with the teachings of the present invention;
FIG. 2 is a cross-sectional view of the fabric depicted in FIG. 1
along line 2--2;
FIG. 3a is a cross-sectional view of the fabric depicted in FIG. 1
along line 3--3;
FIG. 3b is a cross-sectional view of a prior art weave
construction;
FIG. 4a illustrates the yarn orientation in the fabric depicted in
FIG. 1 after the fabric is finished showing only two representative
stacked MD yarns;
FIGS. 4b, 4c, and 4d are a series of illustrations showing the
formation of a seaming loop for the papermakers fabric depicted in
FIG. 1;
FIG. 5a is a perspective view of a prior art MD yarn seaming
loop;
FIG. 5b is a perspective view of an orthogonal MD yarn seaming loop
made in accordance with the present invention;
FIG. 6 is a schematic view of a second embodiment of a fabric made
in accordance with the present invention;
FIG. 7 is a cross-sectional view of the fabric depicted in FIG. 6
along line 7--7;
FIG. 8 is a cross-sectional view of the fabric depicted in FIG. 6
along line 8--8;
FIG. 9 is a perspective view of a portion of the fabric illustrated
in FIGS. 6-8;
FIG. 10 illustrates the yarn orientation in the finished fabric
depicted in FIG. 6 showing the end loop formed by one of the MD
yarns;
FIG. 11 is a top view of the opposing ends of a fabric constructed
in accordance with FIG. 6 just prior to pin-seaming the ends
together;
FIG. 12 is a schematic view of a third alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns;
FIG. 13 is a schematic view of a fourth alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns;
FIG. 14 is a schematic view of a fifth alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns;
FIG. 15 is a schematic view of a sixth alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns;
FIG. 16 is a schematic view of a seventh alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns; and
FIG. 17 is a schematic view of a eighth alternate embodiment of a
fabric made in accordance with the teachings of the present
invention showing only one pair of stacked MD yarns.
DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS
Referring to FIGS. 1, 2, and 3a, there is shown a papermakers dryer
fabric 10 comprising upper, middle and lower layers of cross
machine direction (hereinafter CMD) yarns 11, 12, 13, respectively,
interwoven with a system of MD yarns 14-19 which sequentially weave
in a selected repeat pattern. The MD yarn system comprises upper MD
yarns 14, 16, 18 which interweave with CMD yarns 11, 12 and lower
MD yarns 15, 17, 19 which interweave with CMD yarns 12, 13.
The upper MD yarns 14, 16, 18 define floats on the top surface of
the fabric 10 by weaving over two upper layer CMD yarns 11 dropping
into the fabric to weave in an interior knuckle under one middle
layer CMD yarn 12 and under one CMD yarn 11 and thereafter rising
to the surface of the fabric to continue the repeat of the yarn.
The floats over upper layer CMD yarns 11 of upper MD yarns 14, 16,
18 are staggered so that all of the upper and middle layer CMD
yarns 11, 12 are maintained in the weave.
As will be recognized by those skilled in the art, the disclosed
weave pattern with respect to FIGS. 1, 2, and 3a, results in the
top surface of the fabric having a twill pattern. Although the
two-float twill pattern represented in FIGS. 1, 2, and 3a is a
preferred embodiment, it will be recognized by those of ordinary
skill in the art that the length of the float, the number of MD
yarns in the repeat, and the ordering of the MD yarns may be
selected as desired so that other patterns, twill or non-twill, are
produced.
As best seen in FIGS. 2 and 3a, lower MD yarns 15, 17, 19, weave
directly beneath upper MD yarns 14, 16, 18, respectively, in a
vertically stacked relationship. The lower yarns weave in an
inverted image of their respective upper yarns. Each lower MD yarn
15, 17, 19 floats under two lower layer CMD yarns 13, rises into
the fabric over one CMD yarn 13 and forms a knuckle around one
middle layer CMD yarn 12 whereafter the yarn returns to the lower
fabric surface to continue its repeat floating under the next two
lower layer CMD yarns 13.
With respect to each pair of stacked yarns, the interior knuckle,
formed around the middle layer CMD yarns 12 by one MD yarn, is
hidden by the float of the other MD yarn. For example, in FIGS. 1
and 3a, lower MD yarn 15 is depicted weaving a knuckle over CMD
yarn 12 while MD yarn 14 is weaving its float over CMD yarns 11,
thereby hiding the interior knuckle of lower MD yarn 15. Likewise,
with respect to FIGS. 1 and 3a, upper MD yarn 18 is depicted
weaving a knuckle under yarn CMD yarn 12 while it is hidden by
lower MD yarn 19 as it floats under CMD yarns 13.
The upper MD yarns 14, 16, 18, may be woven contiguous with respect
to each other. This maintains their respective parallel machine
direction alignment and reduces permeability. Such close weaving of
machine direction yarns is known in the art as 100% warp fill as
explained in U.S. Pat. No. 4,290,209. As taught therein (and used
herein), actual warp count in a woven fabric may vary between about
80%-125% in a single layer and still be considered 100% warp
fill.
The crowding of MD yarns 14, 16, and 18 also serves to force MD
yarns 15, 17, 19, into their stacked position beneath respective MD
yarns 14, 16, 18. MD yarns 15, 17, and 19 may be the same size as
MD yarns 14, 16, and 18 so that they are likewise woven 100% warp
fill. This results in the overall fabric having 200% warp fill of
MD yarns.
If the lower MD yarns 15, 17, 19 are also woven 100% warp fill,
they likewise have the effect of maintaining the upper MD yarns 14,
16, 18 in stacked relationship with the respect to lower MD yarns
15, 17, 19. Accordingly, the respective MD yarn pairs 14 and 15, 16
and 17, 18 and 19 are doubly locked into position thereby enhancing
the stability of the fabric.
As set forth in the U.S. Pat. No. 4,290,209, it has been recognized
that machine direction flat yarns will weave in closer contact
around cross machine direction yarns than round yarns. However, a
3:1 aspect ratio was viewed as a practical limit for such woven
yarns in order to preserve overall fabric stability. The present
stacked MD yarn system preserves the stability and machine
direction strength of the fabric and enables the usage of yarns
with increased aspect ratio, in a preferred range of 2:1 to 6:1, to
more effectively control permeability.
The high aspect ratio of the MD yarns translates into reduced
permeability. High aspect ratio yarns are wider and thinner than
conventional flat yarns which have aspect ratios less than 3:1 and
the same cross-sectional area. Equal cross-sectional area means
that comparable yarns have substantially the same linear strength.
The greater width of the high aspect ratio yarns translates into
fewer interstices over the width of the fabric than with
conventional yarns so that fewer openings exist in the fabric
through which fluids may flow. The relative thinness of the high
aspect ratio yarns enables the flat MD yarns to more efficiently
cradle, i.e. brace, the cross machine direction yarns to reduce the
size of the interstices between machine direction and cross machine
direction yarns.
For example, as illustrated in FIG. 3b, a fabric woven with a
single layer system of a flat machine direction warp having a
cross-sectional width of 1.5 units and a cross-sectional height of
1 unit, i.e. an aspect ratio of 1.5:1, is shown. Such fabric could
be replaced by a fabric having the present dual stacked MD yarn
system with MD yarns which are twice the width, i.e. 3 units, and
half the height, i.e. 0.5 units. Such MD yarns thusly having a
fourfold greater aspect ratio of 6:1, as illustrated in FIG.
3a.
The thinner, wider MD yarns more efficiently control permeability
while the machine direction strength of the fabric remains
essentially unaltered since the cross-sectional area of the MD
yarns over the width of the fabric remains the same. For the above
example, illustrated by FIGS. 3a and 3b, the conventional single MD
yarn system fabric has six conventional contiguous flat yarns over
9 units of the fabric width having a cross-sectional area of 9
square units, i.e. 6*(1u.*1.5u.). The thinner, wider high aspect
ratio yarns, woven as contiguous stacked MD yarns, define a fabric
which has three stacked pairs of MD yarns over 9 units of fabric
width. Thus such fabric also has a cross-sectional area of 9 square
units, i.e. (3*(0.5u.*3u.))+(3*(0.5u.*3u.)), over 9 units of fabric
width.
In one example, a fabric was woven in accordance with FIGS. 1, 2
and 3, wherein the CMD yarns 11, 12, 13 were polyester monofilament
yarns 0.6 mm in diameter interwoven with MD yarns 14-19 which were
flat polyester monofilament yarns having a width of 1.12 mm and a
height of 0.2 mm. Accordingly, the aspect ratio of the flat MD
yarns was 5.6:1. The fabric was woven at 48 warp ends per inch with
a loom tension of 40 pli (pounds per linear inch) and 12.5 CMD pick
yarns per inch per layer (three layers).
The fabric was heat set in a conventional heat setting apparatus
under conditions of temperature, tension and time within known
ranges for polyester monofilament yarns. For example, conventional
polyester fabrics are heat set within parameters of 340.degree.
F.-380.degree. F. temperature, 6-15 pli (pounds per linear inch)
tension, and 3-4 minutes time. However, due to their stable
structure, the fabrics of the present invention are more tolerant
to variations in heat setting parameters.
The fabric exhibited a warp modulus of 6000 psi (pounds per square
inch) measured by the ASTM D-1682-64 standard of the American
Society for Testing and Materials. The fabric stretched less that
0.2% in length during heat setting. This result renders the
manufacture of fabrics in accordance with the teachings of the
present invention very reliable in achieving desired dimensional
characteristic as compared to conventional fabrics.
The resultant heat set fabric had 12.5 CMD yarns per inch per layer
with 106% MD warp fill with respect to both upper and lower MD
yarns resulting in 212% actual warp fill for the fabric. The
finished fabric has a permeability of 83 cfm as measured by the
ASTM D-737-75 standard.
As illustrated in FIG. 4a, when the fabric 10 is woven the three
layers of CMD yarns 11, 12, 13 become compressed. This compression
along with the relatively thin dimension of the MD yarns reduces
the caliper of the fabric. Accordingly, the overall caliper of the
fabric can be maintained relatively low and not significantly
greater than conventional fabrics woven without stacked MD yarn
pairs. In the above example, the caliper of the finished fabric was
0.050 inches.
It will be recognized by those of ordinary skill in the art that if
either top MD yarns 14, 16, 18 or bottom MD yarns 15, 17, 19 are
woven at 100% warp fill, the overall warp fill for the stacked
fabric will be significantly greater than 100% which will
contribute to the reduction of permeability of the fabric. The
instant fabric having stacked MD yarns will be recognized as having
a significantly greater percentage of a warp fill than fabrics
which have an actual warp fill of 125% of non-stacked MD yarns
brought about by crowding and lateral undulation of the warp
strands. The fabric may be woven having 100% fill for either the
upper or lower MD yarns with a lesser degree of fill for the other
MD yarns by utilizing yarns which are not as wide as those MD yarns
woven at 100% warp fill. For example, upper yarns 14, 16, 18 could
be 1 unit wide with lower layer yarns 15, 17, 19 being 0.75 units
wide which would result in a fabric having approximately 175% warp
fill.
Such variations can be used to achieve a selected degree of
permeability. Alternatively, such variations could be employed to
make a forming fabric. In such a case, the lower MD yarns would be
woven 100% warp fill to define the machine side of the fabric and
the upper MD yarns would be woven at a substantially lower
percentage of fill to provide a more open paper forming
surface.
The stacked pair MD weave permits the formation of orthogonal
seaming loops within MD yarns. With reference to FIGS. 4a-d, after
the fabric has been woven and heat set (FIG. 4a), CMD yarns are
removed leaving the crimped MD yarns 14, 15 exposed (FIG. 4b). One
of the yarns, for example, MD lower yarn 15, of the stacked pair is
trimmed back a selected distance leaving the other exposed MD yarn
14 of the MD yarn pair and vacated space between the CMD yarns, as
illustrated in FIG. 4c. Upper MD yarn 14 is then backwoven into the
space vacated in the weave pattern by lower MD yarn 15 such that a
loop L is formed on the end of the fabric, as illustrated in FIG.
4d. Preferably, between 0.5-5.0 inches of upper layer yarn 14 is
backwoven into the fabric to provide sufficient strength for the
end loop and assure retention of the free end of MD yarn 14 within
the weave of the fabric. The inverted image weave permits the crimp
of the upper MD yarn 14 to match the space vacated by the lower MD
yarn 15 which further enhances the strength of the end loop.
As shown in phantom in FIG. 4d, adjacent yarn pair 16, 17 is
processed in a similar manner. However, when upper yarn 16 is
looped back and backwoven in the fabric, it is pulled against the
CMD yarns. Where the upper MD yarns are woven 100% fill, the
crowding of the yarns secure the orthogonal orientation of the
seaming loops.
To achieve a uniform seam for a fabric woven in accordance with the
weave pattern depicted in FIG. 1, each upper MD yarn 14 forms a
loop and the other upper MD yarns 16, 18 are backwoven against the
endmost CMD yarn of the fabric. Thus every third upper MD yarn
defines a loop such that an array of loops is created on each end
of the fabric. The seam is assembled by intermeshing the opposing
arrays of loops and inserting a pintle yarn between the intermeshed
loops.
Preferably, loop forming yarns 14 would all be backwoven
approximately the same distance within the fabric to provide
sufficient strength to prevent the loops from being pulled apart
during normal usage. Non-loop forming yarns 16, 18, would
preferably be backwoven a somewhat shorter distance since during
usage no load is imparted to those yarns. For example, upper MD
yarns 14 would be backwoven approximately 3 inches, MD yarns 16
would be backwoven approximately 2 inches, and MD yarns 18 would be
backwoven approximately 1 inch. Respective lower layer yarns 15,
17, 19 would be trimmed to complement the backweaving of their
respective MD yarn pair yarns 14, 16, 18.
FIGS. 5a and 5b, respectively, illustrate a conventional seaming
loop 50 in comparison with an orthogonal seaming loop L of the
present invention. In conventional loop forming techniques, the MD
yarn 51 is backwoven into the fabric adjacent to itself thereby
inherently imparting twist and/or torque to the loop structure 50.
In the present invention, the MD yarn is looped directly beneath
itself and does not have any lateral offset which would impart such
twist or torque to the seaming loop.
Referring to FIGS. 6, 7 and 8, there is shown a second preferred
embodiment of a fabric 20 made in accordance with the teachings of
the present invention. Papermakers fabric 20 is comprised of a
single layer of CMD yarns 21a, 21b interwoven with a system of
stacked MD yarns 22-25 which weave in a selected repeat pattern.
The MD yarn system comprises upper MD yarns 22, 24 which define
floats on the top surface of the fabric 20 by weaving over three
CMD yarns, under the next one CMD yarn 21a to form a knuckle, and
thereafter returning to float over the next three CMD yarns in a
continuation of the repeat.
Lower MD yarns 23, 25, weave directly beneath respective upper MD
yarns 22, 24 in a vertically stacked relationship. The lower MD
yarns weave in an inverted image of their respective upper MD
yarns. Each lower MD yarn 23, 25 floats under three CMD yarns,
weaves upwardly around the next one CMD yarn 21a forming a knuckle
and thereafter continues in the repeat to float under the next
three CMD yarns.
As can be seen with respect to FIGS. 6 and 8, the knuckles formed
by the lower MD yarns 23, 25 are hidden by the floats defined by
the upper MD yarns 22, 24 respectively. Likewise the knuckles
formed by the upper MD yarns 22, 24 are hidden by the floats of the
lower MD yarns 23, 25 respectively.
The caliper of the fabric proximate the knuckle area shown in FIG.
8, has a tendency to be somewhat greater than the caliper of the
fabric at non-knuckle CMD yarns 21b, shown in FIG. 7. However, the
CMD yarns 21a around which the knuckles are formed become crimped
which reduces the caliper of the fabric in that area as illustrated
in FIG. 8. Additionally, slightly larger diameter CMD yarns are
preferably used for CMD yarns 21b, shown in FIG. 7, which are not
woven around as knuckles by the MD yarns to eliminate any
difference in fabric caliber. Preferably the diameter of the larger
CMD yarn 21b equals the diameter d of the smaller CMD yarns 21a
plus the thickness t of the MD yarns.
In one example, a fabric was woven in accordance with FIGS. 6-9,
wherein the CMD yarns 21a, 21b were polyester monofilament yarns
0.6 mm and 0.8 mm, respectively, in diameter interwoven with MD
yarns 22-25 which were flat polyester monofilament yarns having a
width of 1.12 mm and a height of 0.2 mm. Accordingly, the aspect
ratio of the flat MD yarns was 5.6:1. The fabric was woven at 48
total warp ends per inch with a loom tension of 40 pli (pounds per
linear inch) and 20 CMD total pick yarns per inch. The permeability
averaged 90 cfm in the resultant fabric.
In another example, fabric was woven in accordance with FIGS. 6, 7
and 8, wherein the CMD yarns 21a, 21b were polyester monofilament
yarns 0.7 mm in diameter interwoven with MD yarns 22-25 which were
flat polyester monofilament yarns having a width of 1.12 mm and a
height of 0.2 mm. Accordingly, the aspect ratio of the flat MD
yarns was 5.6:1. The fabric was woven at 22 CMD pick yarns per
inch. The fabric was heat set using conventional methods. The
fabric exhibited a modulus of 6000 psi. The fabric stretched less
than 0.2% in length during heat setting. The resultant fabric had
22 CMD yarns per inch with 106% MD warp fill with respect to both
upper and lower MD yarns resulting in 212% actual warp fill for the
fabric. The finished fabric had a caliper of 0.048 inches and an
air permeability of 60 cfm.
As best shown in FIG. 9, the high aspect ratio yarns 22-25
effectively brace the CMD yarns 21a in the weave construction. This
bracing effect can be quantified in terms of the degree of contact
arc .theta. and contact bracing area, CBA, as follows: ##EQU1##
where d=diameter of the CMD yarn
.theta.=the degree of arc over which there is contact between the
MD and CMD yarns
w=width Of the MD yarn
.pi.=the constant pi.
The degrees of arc over which MD yarns 22-25 are in contact with
CMD yarns 21a is dependent upon the spacing of the CMD yarns within
the weave. For the above example, employing alternating 0.6 mm and
0.8 mm diameter CMD yarns with 0.2 mm thick MD yarns, the degree of
contact arc can be maintained in a preferred range of between
60.degree. to 180.degree. by varying the pick count of the CMD
yarns from 14 picks per inch to a maximum of 28.22 picks per
inch.
In the preferred embodiment where the pick count is 20 picks per
inch, the degree of contact arc .theta. is approximately
101.degree.. This results in a bracing contact area of
approximately 0.79 mm.sup.2 at each knuckle in the fabric.
Applicant's use of high ratio aspect yarns, i.e. yarns having a
width:thickness ratio of at least 3:1, provides for increased
bracing contact of the flat MD yarns with the CMD yarns 21a. This
is comparatively exemplified by modifying the equation for contact
bracing area, CBA, to be defined in terms of the thickness of the
MD yarns.
Since the MD yarn width w equals the thickness t of the MD yarn
multiplied by the aspect ratio, w>3t for yarns having an aspect
ratio greater than 3:1. Accordingly, fabrics made in accordance
with the teachings of the present invention utilizing high aspect
ratio MD yarns exhibit enhanced bracing of the CMD yarns by the MD
yarns such that: ##EQU2##
The single layer fabric structure depicted in FIGS. 6-9 is
particularly useful in the creation of a true two-sided, dual
characteristic fabric. This is accomplished by using one type of
yarn for the upper MD yarns 22, 24 and a different type of yarn for
the lower MD yarns 23, 25. Additionally, a third type of yarn may
be used for the CMD yarns which are essentially shielded from both
the machine side and the paper carrying side of the fabric by the
upper and lower layers of warp yarns.
In a preferred embodiment of a single layer, two-sided, dual
characteristic papermakers fabric having the structure disclosed in
FIGS. 6-8, three different types of yarns are used. Yarns made of
nylon 6, 6 with heat stabilizer, which are commercially available
from Asten Monotech, Inc., are used for the upper paper carrying MD
layer yarns. Yarns made of polyester (PET) with hydrolysis additive
are utilized for the lower machine side MD yarns. A
hydrolysis-resistant yarn made of polyphenylene sulfide (PPS),
commercially available from Shakespeare Corporation as HPA-40, or
yarn made of polycycloterephthalate acid resin (PCTA) available
from Albany International, Inc. are utilized for the CMD yarns.
Such a combination of yarn types is particularly suited for the
construction of a dryer fabric which is subject to a variety of
heat and moisture environmental factors. Polyester yarns are
particularly susceptible to hydrolytic action. Accordingly,
polyester yarns are placed on the machine side and protected by the
nylon, paper carrying side of the fabric which is recognized as
having hydrolysis resistance superior to that of polyester. Yarns
such as HPA-40, also known as Ryton.TM. are relatively inert to
hydrolysis. However, Ryton.TM. yarns are prone to abrasion and are
presently more costly than Nylon or polyester yarns. In the CMD
position, the Ryton.TM. yarns are protected from abrasion and
enhance the hydrolysis resistance of the fabric.
Polycycloterephthalate acid resin (PCTA) is less expensive than
Ryton.TM. and also possess hydrolysis resistance superior to
polyester.
Preferably, for a dryer fabric application where a relatively low
permeability fabric of 70-150 cfm is desired, the geometry of the
upper layer nylong 6, 6 yarns 22, 24 and lower layer polyester MD
yarns 23, 25 are both 0.25 mm by 1.06 mm and the size of the
Ryton.TM. CMD yarns alternates between 0.55 mm and 0.80 mm for
yarns 21a and 21b, respectively. The fabric is woven with a total
of 48 MD yarn ends per inch, 24 top layer and 24 bottom layer ends,
with the CMD yarns woven 16-22 yarns per inch. The fabric is heat
set at a tension in the range of 8-15 pounds per linear inch
preferably utilizing the upper end of the range to achieve the
smoothest surface. Preferably, a hot oil cylinder method of heat
setting at a speed of about 3 feet per minute, with a temperature
no greater than 360 degrees is used where the polyester surface is
in contact with the cylinder. However, conventional hot air oven
heat setting may also be utilized.
For a dryer fabric application where a relatively high permeability
fabric of 200-400 cfm is desired, the geometry of the upper layer
nylon 6, 6 yarns 22, 24 and lower layer polyester MD yarns 23, 25
are both 0.30 mm by 0.80 mm and the size of the Ryton.TM. CMD yarns
alternates between 0.50 mm and 0.80 mm for yarns 21a and 21b,
respectively. The fabric is woven with a total of 48 MD yarn ends
per inch, 24 top layer and 24 bottom layer ends, with the CMD yarns
woven 16-24 yarns per inch.
Although the number of MD ends per inch is the same as the low
permeability fabric, the difference in cross-sectional dimensions
of the MD yarns results in the high permeability fabric having a
warp fill of about 75% in each MD layer in contrast to the 100%
warp fill of the low permeability fabric.
The fabric is heat set at a tension in the range of 8-15 pounds per
linear inch preferably utilizing the upper end of range to achieve
the smoothest surface. Preferably, a hot oil cylinder method of
heat setting at a speed of about 3 feet per minute, with a
temperature no greater than 360 degrees is used where the polyester
surface is in contact with the cylinder. However, conventional hot
air oven heat setting may also be utilized.
For wet press felts and forming applications, different types of
yarns may be used for the upper MD yarns, lower MD yarns, and CMD
yarns respectively to achieve desired characteristics. Such
characteristics may be dictated by both physical and economic
reasons in the design of fabric. In some instances it may be
desirable to have different types of yarns dispensed within the
same MD layer or CMD layer.
As best seen in FIG. 10, seaming loops are formed by upper MD yarns
22. The respective lower MD yarns 23 are trimmed a selected
distance from the fabric end and the upper MD yarns 22 are
backwoven into the space vacated by the trimmed lower MD yarns
23.
Upper MD yarns 24 are similarly backwoven into the space vacated by
trimming back lower MD yarns 25. However, as best seen in FIG. 10,
upper MD yarns 24 are backwoven against the endmost CMD yarn
21b.
As illustrated in FIG. 11, a series of seaming loops is formed on
each of the opposing fabric ends 27, 28. When the fabric is
installed on papermaking equipment, the respective end loops formed
by MD yarns 22 are intermeshed and a pintle 30 is inserted
therethrough to lock the intermeshed series of loops together.
Since the seaming loops L are formed by backweaving MD yarns 22
directly beneath themselves, no lateral twist or torque is imparted
on the loop and the loops are orthogonal with the plane of the
fabric. This facilitates the intermeshing of the loop series of the
opposing fabric ends 27, 28. The orthogonal loops are particularly
advantageous where, as shown in FIG. 10, the MD yarns 22, 24 are
100% warp fill and adjacent loops are separated by individual MD
yarns of the same width as the loop MD yarns 22. Lateral torque or
twist on the seaming loops make the seaming process more difficult
particularly where the loop-receiving gaps between the loops of one
fabric end are essentially the same width as the loops on the
opposing fabric end and vice versa.
With reference to the fabric depicted in FIGS. 6-11, the loop
forming MD yarns 22 are preferably backwoven approximately 2 inches
while the non-loop forming MD yarns 24 are preferably backwoven 1
inch.
Alternatively, the seaming loops may be formed in a similar manner
from lower MD yarns 23. In such case, upper MD yarns 22 would be
trimmed back a selected distance from the end of the fabric
permitting the lower MD yarns 23 to be backwoven in the space
vacated by the upper MD yarns 22. This alternative may be preferred
in the case where different types of yarns are used for the upper
and lower MD yarns respectively. In such case, due to the selection
of yarn material, the lower MD yarns may provide better physical
properties for the seaming loops.
With reference to FIG. 12, a third embodiment of a papermakers
fabric 30 is shown. Fabric 30 comprises a single layer of CMD yarns
31 interwoven with stacked pairs of flat monofilament yarns in a
selected repeat pattern. For clarity, only one pair of stacked MD
yarns is shown comprising upper MD yarn 32 and lower MD yarn 33.
The upper MD yarns weave in a float over two CMD yarns 31, form a
single knuckle under the next CMD yarn 31 and thereafter repeat.
Similarly the lower MD yarns weave in an inverted image of the
upper MD yarns weaving under two CMD yarns 31, forming a knuckle
over the next CMD yarn 31 and then returning to the bottom surface
of the fabric in the repeat. Since the repeat of both the upper and
lower MD yarns is with respect to three CMD yarns 31, a total of
three different stacked pairs of yarns comprise the weave pattern
of the MD yarn system.
A fabric was woven in accordance with FIG. 12 wherein the CMD yarns
31 were polyester monofilament yarns 0.7 mm in diameter interwoven
with MD yarns which were flat polyester monofilament yarns having a
width of 1.12 mm and a height of 0.2 mm. Accordingly, the aspect
ratio of the flat MD yarns was 5.6:1. The fabric was woven 48 warp
ends per inch under a loom tension of 60 pli and 18 CMD pick yarns
per inch. The fabric was heat set using conventional methods. The
fabric exhibited a modulus of 6000 psi. The fabric stretched less
than 0.2% in length during heat setting. The resultant fabric had
18 CMD yarns per inch with 106% MD warp fill with respect to both
upper and lower MD yarns resulting in 212% actual warp fill for the
fabric. The finished fabric having a caliper of 0.046 inches and an
air permeability of 66 cfm.
With reference to FIG. 13, a fourth embodiment of a papermakers
fabric 40 is shown. Fabric 40 comprises upper, middle and lower
layers of CMD yarns 41, 42, 43, respectively, interwoven with
stacked pairs of flat monofilament yarns in a selected repeat
pattern. For clarity, only one pair of stacked MD yarns is shown
comprising upper MD yarn 44 and lower MD yarn 45. The upper MD
yarns weave in a float over two upper layer CMD yarns 41, under the
next yarn 41 and a middle layer yarn 42 to form a single knuckle,
under the next CMD yarn 41 and thereafter rise to the top surface
to continue to repeat. Similarly, the lower MD yarns weave in an
inverted image of the upper MD yarns weaving under two lower layer
CMD yarns 43 over the next CMD yarn 43 and a middle CMD yarn 42
forming a knuckle, over the next CMD yarn 43 then returning to the
bottom surface of the fabric to repeat. Since the repeat of both
the upper and lower MD yarns is with respect to four upper and
lower CMD yarns 41, 43, respectively, a total of four different
stacked pairs of yarns comprise the weave pattern of the MD yarn
system.
A fabric was woven in accordance with FIG. 13, wherein the upper
and lower layer CMD yarns 41, 43 were nylon-sheathed, multifilament
polyester yarns 0.62 mm in diameter and the middle layer CMD yarns
42 were polyester monofilament yarns 0.5 mm in diameter interwoven
with MD yarns 22-25 which were flat polyester monofilament yarns
having a width of 0.60 mm and a height of 0.38 mm. Accordingly, the
aspect ratio of the flat MD yarns was 1.58:1. The fabric was woven
with 96 warp ends per inch under a loom tension of 40 pli and 15
CMD pick yarns per inch per layer. The fabric was heat set using
conventional methods. The resultant fabric had 15 CMD yarns per
inch per layer with 113% MD warp fill with respect to both upper
and lower MD yarns resulting in 226% actual warp fill for the
fabric. The finished fabric had a caliper of 0.075 inches and an
air permeability of 60 cfm.
FIGS. 14, 15 and 16 illustrate the fifth, sixth and seventh
embodiments of the present invention. FIG. 14 illustrates the weave
of a relatively long float on both sides of the fabric; FIG. 15
illustrates how a stacked pair MD yarn weave can define floats of
different lengths on opposite sides of the fabric; and FIG. 16
illustrates how a stacked pair MD yarn weave can be used to
construct fabrics having MD knuckles on one side of the fabric.
Relatively long floats predominating the surfaces of a dryer fabric
are beneficial for both the paper-carrying side as well as the
machine side of the fabric. On the paper-carrying side, long floats
provide greater contact area with the paper sheet for increased
heat transfer. On the machine side, long floats provide increased
wear surface and contact area to reduce bounce and flutter. The
stacked pair MD yarn weave is versatile in allowing different
surfaces to be defined on the top and bottom sides of the fabric.
Accordingly, fabrics made in accordance with the teachings of the
present invention may be used for other industrial purposes such as
in the drying of sludge.
With respect to FIG. 14, a fabric 50 is illustrated comprising
three layers of yarns 51, 52, and 53 respectively. In this
construction, the MD yarn pairs, such as the pair formed by upper
layer yarn 54 and lower layer yarn 55, define relatively long
floats on both the top and bottom surfaces of the fabric. Upper
yarn 54 weaves over five upper layer CMD yarns 51, drops into the
fabric to form a knuckle under one middle layer CMD yarn 52, weaves
under the next upper layer yarn 51 and thereafter repeats. Lower MD
yarn 55 weaves in an inverted image under five lower layer CMD
yarns 53, rising into the fabric over the next CMD 53 to weave a
knuckle over one middle layer CMD yarn 52 thereafter dropping to
the bottom surface of the fabric to continue its repeat. In such a
construction, six pairs of stacked MD yarns are utilized in the
repeat of the fabric and are sequentially woven in a selected
sequence to produce a desired pattern on the surfaces of the fabric
which will be predominated by the MD yarn floats.
The embodiment shown in FIG. 15 depicts a fabric 60 in which the MD
yarns weave with a five-float repeat on the top fabric surface and
a two-float repeat on the bottom fabric surface. For example, upper
MD yarn 64 interweaves with upper and middle CMD yarns 61, 62 in
the same manner that upper MD yarn 54 weaves with respective CMD
yarns 51, 52 with respect to fabric 50 in FIG. 14. However, lower
MD yarn 65, which forms a stacked pair with upper MD yarn 64,
weaves in a two-float bottom repeat with respect lower and middle
CMD yarns 63, 62. For example, lower MD yarn 65 floats under two
lower layer CMD yarns 63, rises above the next CMD yarn 63 to form
a knuckle over one middle layer CMD yarn 62 and thereafter drops to
the bottom surface of the fabric 60 to continue to repeat. As with
the other embodiments discussed above, the interior knuckles formed
by the lower MD yarns are hidden by the upper MD yarn of the
respective stacked pair and vice-versa.
The construction shown in FIG. 15 permits different surfaces to be
defined on the top and bottom of the fabric while utilizing the
benefits of the stacked MD yarn pairing.
The embodiment shown in FIG. 16 discloses another example of a
fabric 70 having five-float MD yarns predominating the upper
surface of the fabric, but with MD knuckles on the lower surface of
the fabric. This type of construction may be advantageously used to
construct a forming fabric where the upper fabric surface, having
relatively long floats, would be used as the machine side of the
fabric and the knuckled lower surface of the fabric would be used
as the paper forming side.
Fabric 70 includes three layers of CMD yarns 71, 72, 73
respectively which interweave with stacked pairs of MD yarns to
define this construction. Only one pair of stacked pair of MD yarns
74, 75 is depicted for clarity. Upper MD yarn 74 weaves in a
five-float pattern with respect to upper and middle layer CMD yarns
71, 72 in the same manner as upper MD yarn 54 with respect to
fabric 50 shown in FIG. 14. Lower MD yarn 75 weaves three interior
knuckles and three lower surface knuckles with respect to middle
and lower layer CMD yarns 72, 73 under each upper surface float of
its respective MD yarn pair yarn 74. The repeat of the upper MD
yarns is defined with respect to six upper layer CMD yarns 71 and
the repeat of the lower MD yarns is defined with respect to only
two lower layer CMD yarns 73. Accordingly, there are six different
pairs of stacked MD yarns which constitute the MD yarn system
which, as noted above, can be arranged such that a desired pattern
is formed on the upper surface of the fabric.
Generally for stacked pair weaves, the repeat of the upper MD yarns
will be equally divisible by, or an equal multiple of, the repeat
of the lower MD yarns in defining the stacking pair relationship.
For example, with respect to FIG. 12 the repeat of the upper MD
yarns is six upper layer CMD yarns which is equally divisible by
the repeat of the lower MD yarns which is three lower layer CMD
yarns.
With respect to the eighth alternate embodiment shown in FIG. 17, a
fabric 80 is illustrated having a single layer of CMD yarns 81 and
a representative stacked pair of MD yarns 82, 83. Upper MD yarn 82
weaves with two floats over CMD yarns 81 with a repeat occurring
with respect to three CMD yarns 81. Lower MD yarn 83 weaves with
five floats under CMD yarns 81 with a repeat of six CMD yarns 81.
Thus, in fabric 80, the repeat of the upper MD yarns, which is
three, is an equal multiple of the repeat of lower MD yarns, which
is six.
A variety of other weave patterns employing the paired stacked
weave construction of the instant invention may be constructed
within the scope of the present invention. For example, in some
applications it may be desirable to have MD yarn surface floats
over six or more CMD yarns. Such fabrics are readily constructed in
accordance with the teachings of the present invention.
* * * * *